Melt phase behavior of poly(oxyethylene)-poly(oxypropylene) diblock copolymers

The order-disorder transition of a series of symmetric poly(oxyethylene)-po ly(oxypropylene) diblock copolymers was determined via small-angle X-ray sc attering (SAXS) and used to determine the Flory-Huggins interaction paramet er, chi. The chi parameter was determined using both mean field theory and fluctuation theory, and our results are compared to previously reported val ues. In addition, we determined the structure of a number of asymmetric dib locks via SAXS and compare the results with the phase diagram predicted by self-consistent mean field theory, allowing for conformational asymmetry.